The vaccination of domestic and wild animals is well known. Vaccination is normally performed by injection of a vaccine in liquid form from a syringe. Multiple inoculations are sometimes necessary to achieve a desired effect, due to the inability of the animal's body to respond immunologically to the biologically active ingredient after a single application.
An important disadvantage in administering liquid biologically active materials by syringe involves the preparation of the biologically active materials immediately prior to usage. The biologically active materials are often manufactured in concentrated, freeze-dried form and must be reconstituted prior to use of the biologically active material. Also, all liquid biologicals require shaking prior to and during usage. If the product contains live organisms, the dried biological is usually more stabile than the liquid form and can be shipped and stored under refrigerated conditions until reconstituted for use.
When prepared for use in the animal, the user may reconstitute the above biologically active material with a sterile liquid provided by the manufacturer. The reconstituted biologically active materials must be used within a short period of time and the remainder discarded because of their poor shelf life. When reconstitution is not necessary, the user must still shake the biologically active material before and during use. While the quality of the dried biologically active material can be carefully controlled by the manufacturer, the quality and dosage accuracy of the reconstituted biologically active material or the liquid ready-to-use biological active material is limited by the care exercised by the ultimate user.
To solve the above problem as well as the problem of disposing of used needles, syringes and unused contaminated biological products, biodegradable ballistic projectiles containing freeze-dried biologically active materials for intramuscular implantation into living animal bodies were invented. The nature of the ballistic projectiles has been disclosed in U.S. Pat. No. 3,948,263, U.S. Pat. No. 3,982,536, U.S. Pat. No. 4,449,982 and U.S. Pat. No. 4,664,664. These implants generally comprise a non-lethal polymeric projectile having an interior cavity containing freeze-dried, pelleted biologically active material. U.S. Pat. No. 4,326,524 comprises a solid dosage projectile entirely formed of biologically active material.
There is an ever-increasing demand by consumers for a healthful food supply. The beef industry, as voiced by the membership of the National Cattlemen's Association, is "dedicated to improvement of the total quality of the product they produce" and resolves to "encourage the entire beef industry to work promptly toward a goal of increasing the number of animal health products that can effectively and properly be administered in locations other than lean tissue". These statements of policy resulted from the discovery that injection of some biologicals and pharmaceuticals into lean tissue causes lasting blemishes. These blemishes, although not a health threat to consumers, are a cosmetic problem that often result in a trim loss. Manufacturers of biologicals, in particular, have responded to the problem by recommending their products be administered subcutaneously in the neck and shoulder region or have developed lower volume, "less reactive" products for use by either the intramuscular or subcutaneous route. Those biologicals which are licensed only for intramuscular use are increasingly being recommended for neck-site injection to move the products out of the "prime cuts"
Proper subcutaneous administration of biologicals in the neck region can be very difficult if cattle are chute-processed and often are placed inappropriately. Even if proper placement is achieved, persistent subcutaneous swellings still often result, sometimes involving the hide and/or the underlying edible tissue. Due to the known irritant nature of injectable biologicals, particularly, those containing oils or aluminum salts in liquid suspensions, administration of such in the ear of cattle likely causes substantial tissue reactivity which can result in a "drooped" or "down ear". Thus, a substantial need exists for a system that can deliver biologically active materials in a manner that eliminates lean tissue damage to the animal following vaccination without other undesirable effects.